I swap from electric back to mechanical to double check my readings on the electric and then back again to original. A little trouble shooting and talking about the sending unit. Important to match up the ohms between the sending unit and gauge if you are staying original (electric). Overall, switching them around is pretty easy to do.

Copper line with fittings for mechanical
https://a.co/d/aNlAgYO

Electric sending unit I bought should match 1974 to 1982
From Summit: Crown J3212004 (seems to work pretty well)

Ran across this on Jeep Forum - much better example of ohm matching using an image
https://www.jeepforum.com/attachments...

Can't seem to find the image of the chart I show at the end, but this link goes into more detail and tons of other discussions on www.jeepforum.com of the gauges and sending units. Here is one.
https://www.jeepforum.com/threads/86-...